Self-piercing riveting (SPR) is a suitable technology to join various materials and has attracted more attention in the automotive industry. In this work, the effects of forming parameters on the forming qualities and mechanical properties of B1500HS steel/AA5052 aluminum alloy SPR joints were analyzed. The results show that the sheet stack sequence has little influence on the peak tensile load and rigidity of SPR joints. When the steel sheet is placed on the aluminum sheet, the failure displacement, energy absorption, and ductility factor are, respectively, 2.77, 2.13, and 2.28 times larger than those of the joints with the aluminum sheet placed on the steel sheet. The SPR joints with steel sheets placed on aluminum sheets have better mechanical stability. Meanwhile, when the steel sheet is placed on the aluminum sheet, the fatigue life of the joint can be increased by about 98.4%, 88.3%, and 118.1%, respectively, under high, medium, and low fatigue loads. A joint with opposite riveting direction has the optimal fatigue performance and the fatigue life is 1.64 and 2.14 times those of the other two-rivet joints. Generally, the fatigue fractures of aluminum alloy sheets in SPR joints occurred in fatigue tests. The fatigue fracture of a joint with a steel sheet stacked on an aluminum sheet extends uni-directionally to the edge of the sheet from the riveting point, while a symmetric fatigue crack of aluminum occurs for joints with the opposite sequence. The distribution of fatigue cracks is related to fatigue load, and fatigue cracks mainly originate in the fretting wear area of the contact interface between the rivet leg, upper sheet, and lower sheet.
